Although the number of deaths resulting from traffic accidents has been decreasing recently, the number of traffic accidents still remains high. Traffic accidents are attributed to various causes, and one of the causes to trigger traffic accidents is that of a driver driving a vehicle in a careless state. The careless state can be roughly divided into a state in which the driver becomes inattentive to driving by his performing an act other than driving, such as carrying on a conversation and using a mobile phone and a state in which the driver decreases his attention due to fatigue and sleepiness.
It is difficult for a driver himself/herself to prevent fatigue and sleepiness. Therefore, various systems have been proposed for accurately detecting a drowsy of driver or a decrease in wakefulness of a driver, from the standpoint of safety (see, for example, Patent Literatures 1 and 2).
An estimation device described in Patent Literature 1 estimates whether a driver is in a careless state in which the driver's attention has decreased, on the basis of output from an identification device in which input is biological information of the driver and information on the vehicle the driver drives. Specifically, the estimation device performs weighting on the basis of reliabilities of output results, and estimates, as the state of the driver, a result indicated by the majority of the output results from the identification device.
A device described in Patent Literature 2 estimates the degree of sleepiness a driver feels on the basis of, for example, a plurality of feature amounts of information about the driver's eyes, such as time required for a blink and the degree of opening of the eyes.